CASPER, Wyo. (AP) — The Natrona County sheriff's office says an investigation found a 6-year-old girl who was injured on a school bus last month in Bar Nunn was pushed down by two older boys.

Authorities initially said they were investigating a reported sexual assault, but later called it a case of bullying. The report released Thursday the girl suffered injuries to her genitals on Feb. 11 when she fell and hit a piece of metal that holds the bus seat.

She pointed out the boys to her mother the next day and the bus driver identified them. Deputies interviewed three boys, all of whom denied being involved or witnessing an assault.

Sgt. Aaron Shatto says the report was forwarded to the county attorney's office for review.

Superintendent Steve Hopkins says the district also will investigate.